The present invention relates to a furnace closing mechanism for industrial furnaces comprising a furnace door that can be latched to the shell of the furnace, and a heating insulating door made of a thermal insulating material and connected to the inner face of the furnace door. This door fits up to and thereby produces a thermal insulation located in the furnace interior gas-tight seal.
Industrial furnaces for heat treatment or gas treatment of workpieces normally are formed of a cylindrical pressure vessel, one side or end of which is equipped with a furnace door through which the workpieces are charged into and discharged from the interior of the furnace. Inside the furnace is the heated charging chamber, which is shielded on the outside by a thermal insulation. The chamber is usually in the form of a cylindrical pipe or tubular shaped chamber provided with covers and made of graphite felt or graphite laminate. One of these covers of the chamber must also be removable to allow charging to the chamber and discharging from the chamber as well as gas circulation in the furnace during operation.
In vacuum chamber furnaces, particularly in high-pressure chamber furnaces exposed to high gas pressures both in the heating and cooling cycles, the insulating cover must be particularly tight in order to avoid buoyancy currents in the gas between the hearing chamber and the cold furnace shell.
The furnace closing mechanism normally includes a furnace door adapted to be fitted to the furnace shell and a heat-insulating door attached on the inner side of the furnace door and which insulating door renders the thermal insulation of the furnace gastight. Normally, the closing is effected by means of a bayonet joint or closure, so that the furnace closing mechanism must be rotated 15 to 30 degrees when the furnace is opened or closed. Since in the opening and closing operation the heat-insulating door is pressed against the thermal insulation, loss of insulating material in the sealing joint due to friction occurs every time the furnace is opened or closed. As a result, the thermal insulation of the furnace tends to deteriorate and develop leaks after a certain time and must be repaired.
As a rule, high-pressure sinter furnaces have within the thermal insulation a graphite muffle which must also be sealed with a cover.